Plasma processing apparatuses are widely applied in current manufacturing processes of semiconductor integrated circuits, solar cells, flat panel displays and the like. The types of plasma processing apparatuses that have been widely used in the industry include, for example, DC discharge plasma, capacitively coupled plasma (CCP), inductively coupled plasma (ICP), and electron cyclotron resonance (ECR) plasma. Such types of plasma processing apparatuses are currently used in processes such as deposition, etching and cleaning.
In a processing process, in order to improve the product quality, the wafer needs to be pre-cleaned before the deposition process is implemented, such that foreign a matters such as the oxide on surface of the water are removed. Generally, the basic principle of a precleaning chamber is to excite a cleaning gas (e.g., argon, helium or hydrogen) that is injected into the cleaning chamber to fort plasma, thereby performing chemical reaction and physical bombardment on the wafer. Accordingly, the foreign matters on the surface of the wafer may be removed.
FIG. 1 is a structural schematic view of an existing precleaning chamber. FIG. 2 is an enlarged partial view of FIG. 1. Referring to both FIG. 1 and FIG. 2, the precleaning chamber comprises a cavity 8 and a dielectric window 4 disposed at a top of the cavity 8. A base 1 for carrying a wafer 2 is disposed in the precleaning chamber and is connected to a first RF power supply 12 via a first adapter 11, and the dielectric window 4 is an arched top cover made of an insulating material (e.g., ceramic or quartz). A coil 5 is configured above the dielectric window 4, and the coil 5 may be a solenoid coil connected to a second RF power supply 6 via a second adapter 3. Further, in the precleaning chamber, a process assembly 7 is disposed around the base 1. The process assembly 7, the base 1, and the dielectric window 4 together form a process cavity 41, and a space of the cavity 8 below the base 1 is used as a loading/unloading cavity. Further, as shown in FIG. 2, the process assembly 7 forms a gas inlet/outlet passage with a maze structure for the process gas in the loading/unloading cavity to get in and out of the process cavity 41. Further, a gas inlet line 9 is further disposed on the cavity 8 for transporting a process gas into the loading/unloading cavity. Flow directions of the process gas are indicated by the arrows in FIG. 1. The process gas enters the loading/unloading cavity through the gas inlet line 9, and then diffuses upwards. After the flow is homogenized in the maze structure formed by the process assembly 7, the process gas enters the process cavity 41 to be excited to form plasma. The process gas after reaction enters the loading/unloading cavity after passing through the process assembly 7 and is pumped out by a vacuum pump 10.
In practical applications, the following issues inevitably exist in the aforementioned precleaning chamber:
Firstly, the path fir the process gas to enter the process cavity 41 is too long, such that a relatively long time is needed for the process gas to arrive at the process cavity 41, thereby affecting the process efficiency;
Secondly, because an air pressure within the process cavity 41 is greater than an air pressure near an exhaust port of the vacuum pump 10 and the vacuum pump 10 remains in an operation status during the processing process, most of the process gas is directly pumped out by the vacuum pump 10 before entering the process cavity 41. Accordingly, a large amount of the process gas needs to be supplemented continuously via the gas inlet line 9, such that the plasma remains in an excited state and maintains a desired plasma density, resulting in a waste of the process gas.